The choice of basis set for calculations of linear and nonlinear optical properties of conjugated organic molecules in gas and in dielectric medium by the example of p-nitroaniline

In the present work the moderate-size basis sets suggested earlier – [4s3pMd/3sM′p], [5s3pMd/3sM′p] and [6s4pMd/4sM′p], with (M/M′) = (2/0), (2/2), (3/0), (3/3) – are used for the SCF level calculations of static molecular polarizability αij and first hyperpolarizability βijk of para-nitroaniline (PNA) both in gas and in two solvents (chloroform and acetone). Basis set dependencies of the nonlinear optical characteristics of PNA in gas and in condensed phase are shown to exhibit similar tendencies. It is demonstrated that for NLO chromophores, having a dominant π-electron polarization, one can obtain rather reliable results already with the [4s3p2d/3s] basis set. The obtained data are compared with the ones calculated with Dunning aug-cc-pVDZ basis set, these basis sets are shown to be of equal worth to obtain sufficiently reliable estimations of the (hyper)polarizability values, and they may be used in the study of the effect of the dielectric medium on NLO response of organic molecules at the SCF level.